The current state of automotive electronics is maturing rapidly. Designers and manufacturers are driven by a market which constantly demands more functionality, both as a result of the increasing tastes of users and by demands of competition. In particular, automotive electronics has grown quite rapidly as new features are added and old features are upgraded to place them under electronic control. Consequently, complexity of the vehicle interior subsystems in general and wiring in particular is adversely affected. Multiplexing is a choice for designers wishing to both reduce wiring complexity and increase functionality.
As a result, the field of multiplexing is becoming a sophisticated endeavor with many competing systems all trying for attention. At the low end of the multiplexing spectrum there exists those applications which traditionally would not have been contenders for electronic multiplexing. However, advances in electronics have changed that with single wire multiplexing now becoming feasible.
U.S. Pat. No. 4,459,591 issued to Haubner et al. discloses a method and system for communicating between remote-controlled modules utilizing a single communication line, such as a light guide. Pulse sequences having different pulse widths, pulse gap widths and number of pulses are arranged in a predetermined order to form codes for receipt by respective control modules. Although this system utilizes light pulses as the communication medium in order to minimize sensitivity to electrical noise and voltage offsets, such a system is relatively expensive and difficult to integrate into the vehicle assembly process.